The present invention relates to positioning devices for positioning workpieces in general. In particular, the present invention relates to positioning devices for positioning workpieces along translations and through angular rotations about two or more axes of rotation. The present invention also relates to methods and devices for coupling or launching an optical beam into an optical fiber or spatial filter in general. In particular, the present invention relates to devices for aligning an optical fiber with a laser beam in a laser-to-fiber set-up and an optical fiber with an optical beam issued by an optical fiber in a fiber-to-fiber set-up.
There is a trend to miniaturization in many fields of science and technology which require workpieces to be positioned and aligned to a few microns and many times to sub-microns. Such fields include optics, microscopy, semiconductor technology, micro-machining, the life sciences and others.
Recently, a number of sub-micron flexure devices have been developed to provide translation of workpieces and angular or rotational motion of workpieces. These devices enable motion through the deformation of one or more flexure elements, thereby overcoming the problems of friction and backlash and enabling high spatial resolution.
Flexure devices enabling displacement in two or three coordinate include, for example, U.S. Pat. No. 3,585,866 to Ensinger, U.S. Pat. No. 4,382,709 to Brown, U.S. Pat. No. 4,499,778 to Westhaver et al., U.S. Pat. No. 4,691,586 to van Leijenhorst, and the like. However, these devices suffer from the disadvantage that they do not provide independent displacement along different axes since their flexure hinges are not rigid and their deformations are not restricted to one axis.
Turning now to the field of fiber optics, it is well known that the coupling or launching of an optical beam into an optical fiber is problematic because of the small diameter, typically around 1 microns, of the optical fiber's core. It is also well known that two positional requirements determine the coupling efficiency between an optical beam and an optical fiber. First, that the axis of the optical fiber is aligned coincident to the axis of the optical beam. And second, that the endface of the optical fiber is deployed at the global maximum along the axis of the optical beam. In the case of coupling an optical beam issued by a laser, an objective lens is employed for focussing the laser beam to a spot with a diameter as close as possible to that of the optical fiber's core.
Several devices have attempted to achieve a high coupling efficiency in a laser-to-fiber set-up or a fiber-to-fiber set-up. Such devices are described in U.S. Pat. No. 5,208,888 to Steinblatt et al., U.S. Pat. No. 4,451,115 to Nicia et al., U.S. Pat. No. 4,445,753, US SIR H551 to Chaoui et al., and others. Generally speaking, these devices suffer from the disadvantage that the axis of the optical fiber is aligned coincident to the axis of an objective lens during the alignment procedure and not to the axis of the optical beam. This causes a drop in coupling efficiency in most cases because the axis of the optical beam is typically slightly off center from the axis of the objective lens.
There is therefore a need for positioning devices for positioning workpieces along translations and through angular rotations about two or more axes of rotation. In particular, the positioning devices can be employed for in a method for aligning an optical fiber with an optical beam such that the axis of the optical fiber is aligned coincident to the axis of the optical beam and the endface of the optical fiber is deployed at the global maximum along the axis of the optical beam. The positioning devices can be adapted for use in laser-to-fiber set-ups, laser-to-spatial filter set-ups, fiber-to-fiber set-ups and the like.